The Migration of North American Birds 



SECOND SERIES 



XIV. COWBIRDS 



Compiled by Harry C. Oberholser, Chiefly from Data in the Biological Survey 



COWBIRD 



The Cowbird {Molothrus ater), well known as a parasite of small birds, 

 is widely dispersed over the United States, southern Canada, and Mexico. 

 It is divided into three geographic races, all of which occur in the United States. 



The common Eastern Cowbird {Molothrus ater ater), breeds in the United 

 States and Canada, north to Nova Scotia, New Brunswick, central Quebec, 

 and southern Ontario; west to Minnesota, Colorado, and New Mexico; south 

 to central Texas, northern Louisiana, Tennessee, and southern Virginia; and 

 east to the Atlantic coast. It winters north to Massachusetts and Michigan, 

 and south to Florida, Alabama, and Michoacan, central Mexico. 



The Sagebrush Cowbird {Molothrus ater artemisicB) breeds in western 

 North America, north to southern Manitoba, southwestern Mackenzie, and 

 central British Columbia; west to southwestern British Columbia, western 

 Washington, central Oregon, and eastern California; south to south central 

 eastern California, southern Nevada, Utah, Wyoming, and South Dakota; 

 and east to North Dakota and Manitoba. It winters south to Texas, Vera Cruz, 

 and Michoacan, Mexico. 



The Dwarf Cowbird {Molothrus ater obscurus) is resident in Mexico and 

 the southwestern United States, north to southern Louisiana, southern Texas, 

 southwestern New Mexico, southern Arizona, and southern California; and 

 south to Colima, Oaxaca, and Vera Cruz, Mexico. 



In the following tables the records of the Sagebrush Cowbird are desig- 

 nated by an asterisk, while all the rest refer to the common Eastern Cowbird. 



SPRING MIGRATION 



LOCALITY 



French Creek, W. Va 

 Washington, D. C. . 



Cambridge, Md 



Philadelphia, Pa 



Beaver, Pa 



Morristown, N. J.. . . 



Buffalo, N. Y 



Shelter Island, N. Y. 

 Jewett City, Conn. . . 



Providence, R. I 



Boston, Mass 



St. Johnsburv, Vt.. . . 

 Charleston, N. H.. , . 

 Phillips, Maine 



Number 



of years' 



record 



s 

 17 



6 

 17 



9 

 17 



ID 

 13 



24 



8 

 28 

 23 



5 



Average date of 

 spring arrival 



March 25 

 March 19 

 March 24 

 March 24 

 March 22 

 March 22 

 April 3 

 March 25 

 March 28 

 March 28 

 March 30 

 April 9 

 April 13 

 April 15 



Earliest date of 

 spring arrival 



March 8, 1890 

 Rare, winter 

 March 13, 19x5 

 March 12, 1890 

 March 17, 1905 

 Feb. 9, 1887 

 March 20, 1881" 

 Rare, winter 

 March 7, 1894 

 March 17, 1907 

 Rare, winter 

 March 20, 1903 

 March 30, 1902 

 April 7, 1909 



(343) 



